Introduction to new coronavirus diagnostic techniques

Author . . On August 15th, the U.S. Food and Drug Administration (FDA) issued an emergency authorization to allow the public to use a new saliva-based coronavirus (COVID-19) test, named SalivaDirect, developed by the Yale School of Public Health.
is the fifth new saliva-based coronavirus detection method approved by the FDA on April 13 through RUCDR infinite Biologics and its partners at Rutgers University.
Using the SalivaDirect method to detect the new coronavirus, the testee simply loaded their saliva into a sterile vessel, which was then added with a special reagent by medical staff, and then heated it to release the virus genome, and the results were obtained within 24 hours.
tedious and expensive RNA extraction steps, the SalivaDirect approach allows people to get test results faster and cheaper.
, the SalivaDirect method is slightly less sensitive than other methods of testing using RNA extraction devices.
In a unique way, after Yale University in the United States, the Israeli medical facility Sheba Medical Center recently also disclosed a new coronavirus "saliva test", which lasts less than a second, the accuracy of up to 95%, and the cost is lower.
test using this method, the test subject only needs to pour the main component of physiological saline mouthwash into the mouth, mouthwash and then spit back the reagent bottle.
, the tester puts the sample into the detector and connects the computer for testing.
test results can be displayed on a computer screen in less than a second.
this method is mainly for the test subject's saliva spectral analysis, so the detection equipment only needs a slightly larger box than the palm of the hand.
computer, based on the large amount of data and artificial intelligence analysis accumulated in the previous period, the detection algorithm can give the results in time.
clinical trials showed a 95 percent accuracy rate for saliva testing.
compared with the "saliva detection method", nucleic acid detection is still the new coronavirus infection confirmed "gold standard."
treatment for the new coronavirus is still no specific drug, early diagnosis, early isolation, early treatment is the key to prevent the spread of the disease and improve the cure rate.
important role in the diagnosis of coronary pneumonia, the current new coronavirus common laboratory testing projects are mainly nucleic acid and antibody detection.
detection of new coronavirus nucleic acid is a pathogenic detection method.
Nucleic acid is an essential component of all known living organisms, each species has a unique nucleic acid sequence, the use of special means for the characteristic sequence of the new coronavirus nucleic acid detected the new coronavirus RNA, can be identified as a new coronavirus infection.
nucleic acid diagnostic methods use a variety of samples, including oral swabs, throat swabs, nasal swabs, saliva, vesicle syringes, blood, urine and feces or rectal swabs.
based on SARS-CoV found that sample test results varied widely from source to source.
which is taken from the lower respiratory tract specimens, such as the vesicle irrigation lotion, the best detection effect, from the material convenience and positive rate of comprehensive consideration, throat swabs are the most preferred sampling method.
currently approved by the State Drug Administration 2019-nCoV nucleic acid diagnostic kit application methods are fluorescent PCR method, joint probe anchoring polymerization sequencing method and thermostat amplification method.
addition, new laboratory diagnostic methods are being developed, such as Cas nuclease-based diagnostics and nano-hole sequencing.
nucleic acid detection can detect patients in the window, can detect infections early, and is suitable for large-scale population screening.
nucleic acid test positive is the new coronavirus infection confirmed "gold standard", but nucleic acid test negative can not exclude the new coronavirus infection, during the period may be due to poor sample quality, such as oral pharynx and other parts of the respiratory samples, samples collected too early or too late, did not correctly save, transport and process samples, as well as the technology itself, such as virus mutation, PCR inhibition and other reasons leading to "false negative."
antibody detection serological diagnosis is usually based on the serum of the population to be examined as a sample, by detecting antigens or antibodies to diagnose the pathogen.
commonly used methods include immunosorption tests (including ELISA and nucleic acid-adaptor immunosorption tests), collosine gold test notes, indirect immunofluorescence and pathogen separation, and electrochemical luminescence ELISA and magnetic particle chemical luminescence ELISA based on ELISA development.
, the magnetic particle chemical luminescence method is currently approved by the State Drug Administration two 2019-nCoV serological diagnostic kit application method.
The principle of this method is based on immunosorption test, using magnetic nanoparticle technology under the role of magnetic field-rich enzyme-labeled antibody marker antigen-antibody complex, and then added to the enzymatic chemical luminescent substrate to produce optical signals, through the optical quantum detection function of the enzyme marker detection.
than traditional ELISA, the method is highly sensitive, specific, has a wider linear detection range, is more stable in reagents, and has a higher degree of automation.
new coronavirus antibody is the virus invades the human body, stimulates the human immune cells to produce protective immune globulin.
the principle of antigen and antibody-specific binding, new coronavirus antibodies are detected by labeled specific antigens.
by detecting new coronavirus IgM and IgG antibodies in a patient's blood, helping clinicians determine when a patient is infected with the virus.
IgM antibodies are produced 5 to 7 days after viral infection, generally last 2 to 3 weeks, is an acute infection period.
IgG antibodies are produced in viral infections for 10 to 15 days and can last for months or even long periods of time, belonging to the infection in the middle and late stages or in the past.
antibody testing can be used to test nucleic acid results in doubt, or when RT-PCR is not available for auxiliary diagnosis, retrospective diagnosis, or epidemiological studies to understand the human immune status, but also to guide the use of the new coronavirus vaccine.
Antibody detection negative can not rule out new coronavirus infection, antibody detection may be due to the presence of interfering substances in the specimen (such as rheumatoid factors, heteroantant antibodies, supplements, lysolysase, etc.), specimen hemolysis, specimen contaminated by bacteria, specimen solidification incomplete residual fibrinogen and other factors and other factors and "false positive" results.
, due to the existence of a certain window period of serological methods and the sensitivity of the test kit, there will also be "false negative" results.
Compared with a single detection method, the combined detection of nucleic acids and antibodies is an effective detection method for the new coronavirus, but nucleic acid and antibody detection results are still not the only basis for the diagnosis and exclusion of new coronavirus pneumonia, and should be combined with the patient's epidemiological history, clinical symptoms and other laboratory test results.
RNA, which detects viruses, is direct evidence of the presence of the virus, and antibodies detect specific antibodies produced by stimulation in the patient's blood, which is circumstantial evidence.
when nucleic acid detection negative, increase antibody detection, can make up for the nucleic acid detection easy to miss the shortcomings.
nucleic acid testing is used to detect whether a subject is carrying a virus, while antibody testing is used for complementary testing of suspected patients with negative nucleic acid test results, or joint testing with nucleic acid when a suspected case is diagnosed.
A identification diagnosis for diseases, to ensure "good", one for disease screening, to ensure that "no leakage", the two combined testing, comprehensive reading, can improve the detection rate of new coronavirus positive, reduce the risk of social transmission.
Nucleic acid joint antibody test results clinically judge the new coronavirus as a highly contagious and extremely harmful pathogen, has caused a large number of people to appear fever, cough and pneumonia and other symptoms, and even death, while bringing significant economic losses to the world.
to curb the spread of 2019-nCoV and to enable early treatment of patients in the incubation period, rapid and effective early diagnosis techniques are key to overcoming the outbreak.
References: s1. Crushing U.S. Technology! Israel's "saliva detection method" in 1 second can produce results as low as $0.25 Liao Yajin, Yi Cheng, Peng Zhixin, Liao Yang, Yuan enhancement. New Coronavirus Diagnostic Technology Outlook. Military Medicine, 2020, 44 (04): 258-263 plus 268. Yue Xinjie. One of the new coronavirus detections is known. Shanghai Traditional Chinese Medicine, 2020-07-24 (003). (4) How many two of the new crown virus detections are known. Shanghai Traditional Chinese Medicine Daily, 2020-07-31 (003).